Purchased some Air Kings BFQ90 about a year ago and was planning on upgrading fans. Instead i thought of a way to attach a flange on the bottom side of my BFQ 90 so i hope to seem better filtration. All it took was a 6" Flange ($8) and a drill plus some duct tape. If anyone interested ill post some pics but i wanna let you know it can be done with light modification.